Internal combustion engines, such as engines that use the known Otto or diesel cycles, are widely known and commonly used in vehicles used for moving people and goods, such as motor cars, transport and cargo vehicles, including trucks and locomotives. In summary, these engines use a fuel with a high hydrocarbon content, such as fossil fuels or fuels from renewable sources, to transform thermal combustion energy into kinetic energy.
Nowadays, there is increasing concern to reduce emissions from internal combustion engines, which are responsible for a large part of the CO2 released into the atmosphere. Climate change is one of today's key environmental challenges, with potentially serious consequences. This problem is being caused by intensification of the greenhouse effect, which is in turn related to the increased concentration of greenhouse gases (GHG), including carbon dioxide.
In recent years, in order to minimize the emission of gases that are harmful to the environment, such as carbon monoxide (CO), hydrocarbon gases (HC) and nitrogen oxides (NOx), as well as particulate matter and/or other greenhouse gases, a series of different technologies has been integrated into internal combustion engines. The reduction of gas emissions is related, inter alia, to increased thermal efficiency of the engine, and consequently the reduction of specific fuel consumption.
In this regard, the use of technologies such as electronic injection, catalyzers and particle filters is now fairly widespread, and they are practically mandatory in internal combustion engines. Other, more recent technologies, such as direct fuel injection, common rail for engines that use the diesel cycle, and the more extensive use of technologies that have been known for a long time, such as mechanical compressors or turbochargers, are also being used to increase energy efficiency and to meet increasingly stringent emissions standards.
Consequently, combustion engines are developing greater power for a given displacement volume of the piston in the cylinder, commonly referred to as specific power. The efficiency of an Otto-cycle combustion engine in the 1980s averaged 50 hp/L, whereas today this can easily exceed 100 hp/L. This means that the combustion pressure inside the cylinders has increased considerably, which also means that combustion engines are operating under greater mechanical stresses, higher revolutions, and higher temperatures. As such, the components of same also need to be dimensioned to withstand these harsher operating conditions in order to guarantee both the reliability of the assembly and the anticipated service life, currently estimated at around 300,000 km for Otto-cycle motor cars.
One of the components most subjected to the stresses generated by combustion engines are the bushings, used both in bearings such as the bearings of the crankshaft and of the camshaft, etc., and in the connecting rods, and they are used both as supports and to reduce friction. They usually have a two-part construction, i.e. they are formed by two semicircular parts that are superposed on the perimeter of the bearing or of the end of the connecting rod. Bushings are usually made of a softer material in order to reduce friction between such rotating components, and they can also facilitate assembly, withstand assembly misalignments and accommodate particles, as is well known to persons skilled in the art.
However, as mentioned above, the operating conditions of internal combustion engines are becoming increasingly severe, and bushings, which have to withstand the pressure exerted by the connecting rods and/or by the shaft assembled in the bearing, are subject to greater wear. This wear is usually more accentuated in the areas closest to the lateral extremities of the bushing, due to the reduced distribution of oil in these areas. Consequently, bushings usually have an orifice in the central portion of same to enable an oil flow.
Bushing wear is an unwanted effect, since it may lead to play that compromises engine performance, as well as oil leaks and/or consumption.
The present invention is intended to overcome these and other drawbacks.